This invention relates to decreasing the dust loading of the product gas of a pressurized coal gasifier and in particular to decreasing the dust loading of the product gas before the product gas passes through a horizontal crossover duct near the bottom of the enclosure vessel to a convective cooling section.
In present pressurized gasification systems in which a carbonaceous fuel is gasified, the reaction gas together with combustion residues are cooled in a heat exchanger disposed directly beneath the reactor vessel. Heat transfer in the heat exchanger occurs predominantly by means of radiation. Typically, the product gas flows into the heat exchanger from the reactor vessel through an inlet at the top center of the heat exchanger. The product gas flows downward through the heat exchanger, reverses direction and flows upward to exit from the heat exchanger and surrounding vessel through an outlet near the top of the vessel. Typically, there is a body of water disposed in the lower region of the vessel surrounding the heat exchanger to receive and quench particulate matter discharged from the product gas stream as the gas stream reverses direction. The prior art heat exchangers typically have one or more gas outlets near the top of the enclosing vessel which provides a more uniform gas velocity from the region of downward product gas flow radially outward in the region where the product gas reverses direction to flow upward. A plurality of gas exits from the heat exchanger further enhances the uniform radial velocity of the product gas in the region where the flow direction reverses.
It is an object of this invention to provide a heat exchanger having a single gas outlet near the bottom of the heat exchanger that incorporates a product gas flow reversal of at least 180.degree. while maintaining uniform radial gas velocity to enhance particulate matter separation.